1. Field of the Invention
The present invention relates generally to telecommunications systems, and more specifically is directed toward methods of providing prepaid telephony service via an Internet protocol (IP) network system.
2. Description of the Related Art
Prepaid telephony service is a very popular service in the existing Public Switched Telephone Network (PSTN). For example, prepaid calling cards are typically used by PSTN subscribers to place calls. Typically, a user or subscriber of a prepaid calling card initiates a phone call by calling a signaling agent, such as a communications station or server, via a toll-free number (800/888) provided on the prepaid calling card. The subscriber is then prompted to enter his home telephone number and an identification number (PIN) also provided on the prepaid calling card using a telephone keypad.
The signaling agent then proceeds to perform validation procedures to determine if the home telephone number matches the identification number using a look-up table stored within a database or if the identification number is valid. If the two numbers match or if the identification number is valid, then the signaling agent performs database queries to determine if the subscriber's account balance is more than a predetermined amount. If the account balance is more than the predetermined amount, then the signaling agent informs the subscriber of the length of calling time available and indicates to the subscriber to enter a number to be dialed. The signaling agent then proceeds to place the call by transmitting signaling messages to appropriate communications devices along a media path flow, i.e., the path through which call media streams are routed through the PSTN. If the account balance is less than the predetermined amount, then the signaling agent informs the subscriber that a call cannot be placed.
During the duration of the call, the signaling agent monitors the subscriber's account balance. If the account balance falls below the predetermined amount, the signaling agent transmits a message to the subscriber via the same media path flow as the path of the call media streams indicating to the subscriber the amount of available time. After the subscriber's account balance has been depleted, the signaling agent tears down the PSTN call by blocking the media path flow as described below.
In the PSTN, the call is torn down by the signaling agent transmitting a “switch-off” signaling message to a media agent or a routing station along the media path flow through which the call media streams are routed through. The “switch-off” signaling message disables the media agent to prevent the call media streams from being transmitted further along the media path flow. Hence, the PSTN call is torn down.
It is inconsequential if the signaling agent is or is not located along the media path flow, since in the PSTN, signals transmitted to or received from any one station (e.g., a server) can be directed to or received from a variety of other stations or servers within the network. Therefore, in a prepaid calling card scenario, whether or not the signaling agent is located along the media path flow, the signaling agent can effectively control call setup, the duration of the call based on the subscriber's account balance, and call tear down by directing signaling messages to the appropriate media agent or other routing station.
In the case of using an Internet protocol (IP) network system to place a non-prepaid call, with reference to FIG. 1, there is shown an IP network system designated generally by reference numeral 10 having a plurality of media agents, i.e., devices for handling packets through the system 10. In the IP network system 10, call media streams are routed from a telephone 20 through a PSTN telephone switch 30 to an IP telephony switch 40 over an ISDN line. The call media streams are then routed to the IP network 50 over an IP line, and then over a corresponding IP line to a destination IP telephony switch 40′, further to a destination PSTN telephone switch 30′ over an ISDN line and finally to a destination telephone 20′. The call media streams can also be routed from the telephone 20 to an IP terminal 75, such as a personal computer (PC).
The IP telephony switches 40 and 40′ provide basic interfacing between the PSTN telephone switches 30 and 30′ and IP network 50 and include both gateways 60a and 60b, as well as gatekeepers 70a and 70b. Gatekeepers 70a and 70b use the signaling information provided by the gateways 60a and 60b to provide directory services. During a call setup, the originating gatekeeper 70a sets up a communication path between the originating and terminating gateways 60a, 60b by determining the destination gatekeeper 70b associated with a destination IP address or telephone number. The destination gatekeeper 70b selects a destination gateway 60b to complete the IP virtual circuit.
With reference to FIG. 2, an example of a call which originates in the PSTN, traverses the IP network, and terminates back in the PSTN is shown. First, at A, an Internet telephony service subscriber dials an access number provided by the Internet Telephony Service Provider. At B, the call is routed by the PSTN telephone switch 30 to the IP telephony switch 40. The gateway 60a at C plays an announcement requesting that the subscriber enter the destination telephone number to be called. The destination digit information is sent to the gatekeeper 70a. Accordingly, the gatekeeper 70a determines a destination gatekeeper IP address based on the destination digit information. An IP packet requesting the availability status of the destination gateway 60b is sent to the destination gatekeeper 70b at D. The destination gatekeeper 70b responds to the request by providing destination gateway 60b availability and IP address information. The originating gatekeeper 70a then transfers this information to the originating gateway 60a at E.
With continued reference to FIG. 2, at F, the originating gateway 60a sets up a virtual circuit to the destination gateway 60b. This circuit is identified by a call reference variable (CRV) that will be used by both gateways 60a, 60b for the duration of the call to identify all IP packets associated with this particular call. Finally, at G, the destination gateway 60b selects an outgoing PSTN voice trunk and signals to the PSTN switch 30 to attempt to set up a call to the dialed telephone number.
During the call, the packet-switched IP network 50 routes the IP packets associated with the particular call along different routes before reaching the IP telephony switch 40′ or terminal 25 (e.g., a multimedia personal computer (PC) equipped with Session Initiation Protocol (SIP) or H.323 software, a microphone and speakers). SIP and H.323 terminals support the encoding/decoding and packetization/sequencing of information exchanged with other SIP and H.323 terminals or gateways. Packets are routed to the destination IP address contained within the header of each packet and may travel over separate network paths before arriving at their final destination for reassembly and resequencing. Accordingly, the routing of packets within the IP network is different than the routing of the call media streams by the PSTN during a conventional PSTN call, where all the call media streams associated with a particular call are routed along the same media path.
Accordingly, prepaid telephony services cannot be achieved via the IP network shown by FIGS. 1 and 2 and described above, since call signaling messages from a signaling agent, such as a server, do not take the same media path as the call media streams, since the IP network is a packet-based network where each packet from a particular station is routed along a different media path than other packets. Further, with conventional servers and IP network hardware, the call signaling messages cannot be directed or controlled to take the same path as the call media streams.
Therefore, a need exists for a method of having a signaling agent control at least one media agent of an IP network system for allowing and blocking call media streams from traversing through the media agent.
Further, a need exists for a method of directing all signaling messages transmitted by a signaling agent and all media packets transmitting voice and data communications through an IP network system through one media flow path.